Solar Starter Battery Maintainer

[Ayjay]

Does anybody use one of these or have a view? I'm just thinking ahead to possibility of cold winter weather and the impact on a starter battery of a T6 camper parked up in the open that's not going to get used that much. I will be trying to make a point of taking it for the odd blast up and down the motorway just to keep things ticking over but TBH it's never going to be used as my daily ride (which itself is probably not driven enough!).

Alternatively, I tend to leave the van hooked up to the mains at home to keep the leisure battery topped up but I am planning on having a 120 to 150W solar panel fitted to the roof at some point to take care of that in the future and obviate the need for a permanent mains hook up. Does anybody therefore know whether it would be possible for a solar panel to be easily wired so that it tops up both the car and leisure batteries as needed? If it's relevant, the van electrics already include a CTEK 250SA and Victron Blue Smart.

Any advice to a newbie in this stuff (as well as a numpty on all things mechanical and electrical) would be much appreciated.

 

[Dellmassive]

You could use a 50w PWM mobile solar panel on the dash like here >>>> (lower down thread) Mobile Solar Panels ? . . . - How I Did It -

but remember your starter and Leisure battery are isolated . . .

so you could use 2x solar kits . . . one for each battery.

or one solar kit and a battery combiner . . . .

or one solar kit and a - "2A 12V DC TO DC BATTERY TO BATTERY TRICKLE CHARGER" to topup the second battery. like one of these > 12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine

Remember the above is just a Diode and a resistor in a box so dont expect miracles . . .

also your CTEK 250SA has a solar input so you could connect a mobile solar panel to that for your leisure battery. . . . . then use a combiner to send charge to the starter battery.

or

The Ctek also has a nice function of reverse trickle charging that starter from the leisure battery . . .

"Trickle charging of the starter battery from a solar panel The D250SA trickle charges the starter battery from a solar panel at intervals of 3 seconds if the service battery is fully charged."

https://www.ctek.com/storage/ma/b21ecd5d5e5943a995474cf36d586451/956c3913c8cc4319bb4e47baea0c6d82/pdf/A78BBB08A9DF8976DB79E21271E091489ACEF47A/D250SA-manual-UK-EN.pdf

All of the above will rely on a decent solar panel to provide the power . . . . a 50W panel may be fine in summer . . . . . but you might need a premium 100w or larger panel in winter due to the lower solar levels. . . . . . (basically, whatever you do, dont buy a cheap panel if your looking to use it in winter)

 

[t0mb0]

As above, either use the cteks built in starter trickle charger if it will take the voltage of your panel or use a separate “battery master” type box to trickle charge the starter. I have a votronic mppt solar controller which trickle charges the starter (effectively a built in “battery master”) and it’s excellent.

 

[Ayjay]

Dell and tOmbO - Thanks for that. It sounds like I should just keep it plugged into the mains until I sort out a solar panel and then make sure that the installer wires it so that the starter battery also gets a charge via the CTEK jobbie (or does that happen automatically once the panel is connected to the appropriate terminals?)

As a supplementary question, when the van is plugged into the the mains, the meter consistently shows 13.1V as the battery charge but if I go for a drive, it reads 13.9 but then drops back down to 13.1 again after a while (and even after being plugged into the mains again). At no time is anything switched on. Is this normal please?

Again, thanks for the advice.

 

[t0mb0]

Dell and tOmbO - Thanks for that. It sounds like I should just keep it plugged into the mains until I sort out a solar panel and then make sure that the installer wires it so that the starter battery also gets a charge via the CTEK jobbie (or does that happen automatically once the panel is connected to the appropriate terminals?)

As a supplementary question, when the van is plugged into the the mains, the meter consistently shows 13.1V as the battery charge but if I go for a drive, it reads 13.9 but then drops back down to 13.1 again after a while (and even after being plugged into the mains again). At no time is anything switched on. Is this normal please?

Again, thanks for the advice.

The mains charger will use a multi-stage charging profile, a voltage of 13.1v from the charger is very much on the low end and implies that the battery is basically fully charged - I'd expect it could get upto about 14.7v (maybe even more if the battery is cool and the charger has temperature compensation) for a standard AGM charging profile when earlier in the charge process. When the battery is fully charged and then disconnected from the charger, the battery will start out at 13.1v (or whatever the charger was last at) because there is a memory effect in the battery, but it will soon settle down to its natural resting voltage, which is usually about 12.8v for an AGM battery. Any load on the battery will cause voltage sag on the battery so it will naturally decrease as current is pulled from it. As the battery's state of charge diminishes, its resting voltage will also naturally reduce.

When the van is being driven, your ctek250 should take over. It might use a slightly different charging profile from the mains charger but the basic idea is the same so 13.1v-13.9 is well within the range of voltages expected. It's probably using 13.9 for a while, whilst it works out the battery is basically fully charged and then dropping to a maintenance-voltage.

In short, the voltages you describe are all within expectations!

 

[Skyliner33]

@Dellmassive whats a combiner please?

 

[Ayjay]

Thanks guys, that's reassuring (and sorry for the silly questions but this camper van stuff is all new to me!).

 

[Dellmassive]

@Dellmassive whats a combiner please?

Its basically a "split charge relay" . . . . but in this application it would only be used when the engine is NOT running.

it would be wired up so that any solar charger that is topping up the leisure battery would then activate the "combiner/relay" so that the solar charge will also flow to the starter batter.

There basic relay types . . . . and more advanced types that include a blocking diode so that current will only ever flow from the |Leisure battery to the starter battery.

here are a few examples . . . . .

Battery Isolators and Combiners - Victron Energy

Cyrix Battery Combiners - Victron Energy

.